Great job on the hardware and software. A few suggestions:
Include all of the jars you are dependent on or provide an ant target for downloading them.
Have you given any thought to using the RXTX gnu.io classes instead of Sun's? Sun does not support Java Comm API on any platform other than Windows and Solaris. The RXTX gnu.io classes work on Windows, Linux and Mac OS X without any problems.
Include ant targets to set up RXTX and JDOM for each platform.
You should be able to use a single build.xml file for all platforms.